Just like the words we use, the way we spell them and their meanings have changed over time, so too has the way English language is spoken. For as long as English has been a language it has been changing, to the point where English from centuries ago would be virtually unrecognisable. This is because language is always evolving to be more efficient and smooth through techniques that will be discussed below. Over time, English has lost consonants, vowels and even entire syllables in the constant editing process language goes through to achieve efficiency. Sounds can disappear in any context, but they are most prone to loss from the endings of words, where articulation is not as strong. this is evident in the shortening of words that will be discussed in Lexical Changes to English. these shortenings, like 'pro' and 'grotty' are great examples of English losing the endings of words. Sounds can be modified based on the sounds surrounding them by anticipating the sounds after them or being influenced by the sounds before them to change the pronounciation. This concept is known as assimilation. When sounds assimilate they adaopt to become more like the sounds around them while following one or more of three main criteria. These critea being whether the sound is voiced or voiceless (vocal folds) , the place of articulation and the manner of articulation. A clear example of this is when you say the words 'pancake' or 'incompetent' in a sentence the /n/ will be expecting the velar /k/ sound and so assimilate to of it by the place of articulation - so what you end up saying will mostlikely sounds closer to 'pangcake' or 'ingcompetent' (ɪŋkɒmpətənt).The opposite action to assimilation is dissimilation, where sounds become dfferent to the sounds around it, or possibly what it is meant to sound like. This can be attributed to the fact that repetition of the same sounds can be difficult, difficulty with repetitive sounds is most obvious in attempting tongue twisters, like 'she sells sea shells by the sea shore' or 'Peter Piper picked a peck of pickled peppers'. Even tongue twisters as simple as 'red leather yellow leather' can be extremely difficult. These give us a good example of why dissimilation occurs, it's easy to substitute sounds or stumble over words that involve repeating sounds and words. To try more tongue twisters click here. We've already discussed sound loss, and the opposite to this is the phenomenon of sound addition. Vowels can be added to words to make otherwse difficult clusters of sounds smoother and eaiser to say - for example umberella instead of 'umbrella' and athalete instead of 'athlete'. This inclusion of new sounds is also applicable to consonants, however in this case the addition is contributed to a stumble or mistiming while speaking, resulting in unusual pronunciation like fambly rather than 'family'.